1. Field of the Invention
This invention relates to a method for binarizing a gray scale document image, and in particular, it relates to method for binarizing and segmenting a document image using image phase congruency.
2. Description of Related Art
In document processing, there is often a need to generate a binary image from a color or gray scale document image. Sometimes binarization is a part of a process to extract text from the image (referred to as optical character recognition or OCR). For example, a scanner typically scans a hard copy document into a grayscale or color image first, and then performs binarization to generate a binary (pure black and white) image and/or perform OCR to extract textual content from the scanned image. Or, with the widespread use of digital cameras and smart phones, a user can take a picture of a document or an object bearing text or labels, and a process is needed to convert the color or gray scale picture into a binary image and/or to extract the textural content. Often, the document image (the scanned image or picture taken with a camera) includes both text and non-text contents such as images or graphics. A binarization process often needs to distinguish text and non-text contents, and segment the overall document image to separate text and non-text contents.